Lennie made another mistake! He killed Curley's wife! So, he followed G's request and went to the brusLennie made another mistake! He killed Curley's wife! So, he followed G's request and went to the brush to wait for G's coming. At the same time, men from the ranch were all coming to catch him. But the question is Who killed Lennie? Was that really George? There are three sides which are poor police, the pressure from other Ranch Hands and the falling of their dream. They all impel the death of L. 
Because of the weakness and incompetent of the police, no one would have to pay for L's death. When they first see the died body of Curley's wife, Curley said:" I'll kill the big son-of-bitch myself. I'll shoot 'im in the guts." After G killed Lennie, Slim encouraged G that Come on, George. Me an' you'll go in an' get a drink." When the "Ranch Hands" found Curley's wife was killed by L, they went to hunt L. And after Slim discovered Lennie was died already, he invited G to go to drink with him. Now the problem is showed. Instead of going to tell the police, they decided to kill L by themselves. This really unfolds the incompetent of the police. If the police is strong enough, this won't happen, because L did not kill C's wife on purpose. If this happens at present, the judge may not adjudge he to die. But because of the police does not have the prestige to make people trust it and to solve conflicts, L will be killed by the Ranch Hands, and G has to kill L to protect him from the suffering of the other Hands. Thus, police should be a part of pushes which lead L into death. Also this is not the only reason, there are some more pressures impels the death of L.
The pressure from other Ranch Hands is also a push to L's death. Curley is anxious for killing L, and other men are hunting him too. Curley said:" I'll kill the big son-of-bitch myself. I'll shoot 'im in the guts."